1. Field of the Invention
The present invention relates to a liquid level indicator, and more specifically to a structure of supporting a shaft for mounting a liquid level sensor.
2. Description of the Prior Art
Liquid level indicators are used to measure fuel remaining within a fuel tank for an automotive vehicle, for instance, or to generate an alarm signal when fuel remaining within the fuel tank decreases below a predetermined level.
The liquid level alarm indicator is usually composed of an alarm signal generating section and an alarm signal displaying section. In the alarm signal generating section, a thermistor element, a float switch, an electrode, etc. are used to detect the presence or absence of liquid at a predetermined level.
When a thermistor element is used, for instance, since heat dissipation of the thermistor element in fuel is large, self-heating phenomenon will not occur, so that the resistance of the element is relatively high. On the other hand, when fuel level decreases and therefore the thermistor element is exposed to air, since the heat dissipation becomes small, self-heating phenomenon occurs, so that the resistance thereof decreases with increasing temperature to increase circuit current which turns on an alarm lamp.
In the prior-art liquid level indicator, however, a shaft for mounting a liquid level sensor (e.g. thermistor element) is simply fixed to a frame by two screws, when force is applied to the sensor element or the shaft via liquid along various directions, there exists a problem in that thin-wall portions of the sensor shaft through which screws are passed are subjected to deformation. In addition, there exist other problems such that when mechanical or thermal shock is applied to the sensor shaft during assembling, the screws are easily loosened and therefore the sensor shaft becomes loose relative to the frame or is removed from the shaft at the worst.
These drawbacks result in a dislocation of the sensor and therefore deteriorate the reliability of liquid level indication or liquid level alarm indication. Furthermore, the looseness of the sensor shaft relative to the frame will cause noise within the fuel tank when the tank is vibrated.
The arrangement of the prior-art sensor shaft supporting structure for liquid level indicators will be described in further detail hereinafter with reference to the attached drawing under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.